Home Page of  Erfan Baghani (Ph.D.)
Erfan Baghani Photo

Welcome



Welcome to my home page. I am a post-doctoral research fellow at the University of British Columbia. In my home page, you can find brief descriptions for the research projects I have worked on. A list of my publications emanating from these research projects is available under the Publications tab above. You can find my educational background under the Education tab. I have also provided my emaill address under the Contact tab.





Education History


  • Part time studies in Mobile and Web Development, British Columbia Institute of Technology, Vancouver, Canada, July 2016 – July 2018
  • Ph.D. in Electrical Engineering, The University of British Columbia Okanagan, Kelowna, Canada, May 2009 – November 2012
  • Ph.D. in Physics, University of Windsor, Windsor, January 2008 –April 2009
  • M.Sc. in Physics, Sharif University of Technology, Tehran, Iran, September 2005–November 2007
  • B.Sc. in Physics, Sharif University of Technology, Tehran, Iran, Septemebr 2001–September 2005
  • High School Diploma , Allaame Helli High School, Tehran, Iran, September 1997–March 2001

Links to the websites of my educational institutions



  








Electrical Properties of Dislocations within the Nitride Based Semiconductors GaN and InN

Energy band structures within GaN and InN Figure

The nitride based semiconductor material gallium nitride (GaN) along with its ternary and quaternary alloys with aluminum nitride (AlN) and indium nitride (InN) has found an increasingly diverse range of applications in the electronics and optics industries over the last couple of decades. Unlike the more traditional semiconductor materials such as silicon, germanium, and gallium arsenide, obtaining high quality crystals of the nitride based semiconductors remains an outstanding challenge. Epitaxially grown crystals of the nitride based semiconductors exhibit a high concentration of one dimensional defects extending from the substrate material all the way into the grown crystal. These one dimensional defects are generally referred to as the threading dislocation lines. The presence of these threading dislocation lines degrades various aspects of semiconductor device performance. As a result, an understanding of the electrical properties of the threading dislocation lines within the nitride based semiconductors can have direct implications for the optimization of GaN electronic device performance. In our research we have investigated the effect these threading dislocation lines within the nitride based semiconductors have on (i) the free carrier concentration and (ii) the electron mobility, as two of the most important underlying physical parameters influencing semiconductor device performance.

Carrier Cooling Dynamics in Colloidal CdSe Nanoplatelets

Carrier Cooling Figure

In recent years nanoplatelets of the semiconducting material cadmium selenide (CdSe) have been synthesized chemically with atomic layer control over the thickness of the platelets. The resultant tunability in the luminescence wavelength of the platelets along with a high quantum yield and the direct nature of their energy gap make these nanoplatelets particularly promising structures for optical applications over a wide range of the electromagnetic spectrum. On the experimental front, our collaborators have synthesized CdSe nanoplatelets with different layer thicknesses. They have subsequently used a femtosecond ultrafast laser light to excite electrons from the valence band into the conduction band of the platelets. Within these nano-sized platelets the electrons excited by the incident laser beam become bound to the holes they leave behind in the valence band, thereby forming excitons (bound electron-hole pairs). The extra energy - over the exciton formation energy - added by the photons in the incident laser beam gets distributed as thermal energy among the free carriers within each platelet. An analysis of the time-resolved photoluminescence data indicates that the carriers reach internal thermal equilibrium on sub-picosecond time scales after the laser light incidence. Following this initial internal equilibrium phase, the free carrier system cools down to near room temperature on a time scale of several hundred picoseconds. On the theoretical front, we have analyzed the temporal evolution of the spectrally integrated photoluminescence intensity data as well as the carrier temperature data derived at different pump fluences of the incident laser beam. From this analysis we have been able to identify the underlying physical processes involved in the cooling of the carriers within the platelets.

Electron Transport within the ZnO/ZnMgO Heterojunction

2DEG ZnMgO-ZnO band discontinuity figure

Modulation doped field effect transistors (MODFETs), also known as high-electron-mobility transistors (HEMTs), are among the fastest transistor designs to have been innovated in the semiconductor industry. They incorporate a junction between two materials with different band gaps (i.e. a heterojunction) as the channel. The functionality of these transistors relies on the formation of a very thin layer of highly mobile conducting electrons - also referred to as a two dimensional electron gas (2DEG) - with very high concentration within the lower band gap region of the junction. The most common semiconductor material combinations employed for the fabrication of HEMTs are gallium arsenide/aluminum gallium arsenide (GaAs/AlGaAs) and gallium nitride/aluminum gallium nitride (GaN/AlGaN). In recent years, the zinc oxide/zinc magnesium oxide (ZnO/ZnMgO) heterostructure has also emerged as a promising candidate for the manufacturing of the next generation HEMTs. In our research, we have investigated how variations in the free electron concentration in relation to the doping concentration in the ZnO region of this heterojunction affects the low field electron mobility in this material system. We have also studied the steady state and transient response of electrons to the sudden application of an electric field within this material system.







Journal Articles

  • “Auger-Limited Carrier Recombination and Relaxation in CdSe Colloidal Quantum Wells”, Erfan Baghani, Stephen K. O’Leary, Igor Fedin, Dmitri V. Talapin, and Matthew Pelton, J. Chem. Phys. Lett., 6, 1032 (2015)
  • “Occupation statistics of the 5/7-atom dislocation core structure within n-type indium nitride”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys., 114, 053705 (2013)
  • “An enhancement in the low-field electron mobility associated with a ZnMgO/ZnO heterostructure: The role of a two dimensional electron gas”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys., 114, 023703 (2013)
  • “A transition in the nature of the occupancy of the dislocation lines within n-type wurtzite gallium nitride”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys., 113, 163501 (2013)
  • “Dislocation line charge screening within n-type gallium nitride”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys., 113, 023709 (2013)
  • “Electron mobility limited by scattering from screened positively charged dislocation lines within indium nitride”, Erfan Baghani and Stephen K. O’Leary, Appl. Phys. Lett. 99, 262106 (2011)
  • “Occupation statistics of the dislocations within n-type gallium nitride”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys., 110, 033509 (2011)
  • “Occupation statistics of dislocations within uncompensated n-type wurtzite gallium nitride”, Erfan Baghani and Stephen K. O’Leary, J. Appl. Phys. 109, 113706 (2011)

Conference Articles

  • “Semiconductor nanoplatelets: a new colloidal system for low-threshold high-gain stimulated emission”, Matthew A. Pelton, Chunxing She, Igor Fedin, Dmitriy Dolzhnikov, Sandrine Ithurria, Erfan Baghani, Stephen K. O'Leary, Arnaud Demortiere, Richard D. Schaller, Dmitri V. Talapin, SPIE Nanoscience+ Engineering, pages 954503-954503-1, 2015.
  • “Electron transport within a zinc-oxide-based two-dimensional electron gas: The impact of variations in the electron effective mass”, Walid A. Hadi, Erfan Baghani, Michael S. Shur, and Stephen K. O’Leary, Materials Research Society Spring Meeting Proceedings, Volume 1674, pages J-08-19-1-6, 2014.
  • “Electron transport within the two-dimensional electron gas formed at a ZnO/ZnMgO heterojunction: Recent Progress”, Walid A. Hadi, Erfan Baghani, Michael S. Shur, and Stephen K. O’Leary, Materials Research Society Spring Meeting Proceedings, Volume 1577, pages XX-03-23-1-6, 2013.
  • “The occupancy of the threading dislocation lines within n-type gallium nitride: Recent progress”, Erfan Baghani and Stephen K. O’Leary, Materials Research Society Spring Meeting Proceedings, Volume 1432, pages G-07-07-1-6, 2012.

Theses

  • Erfan Baghani, “Electrical properties of dislocations within the nitride based semiconductors gallium nitride and indium nitride", Doctoral dissertation, The University of British Columbia, 2012. http://hdl.handle.net/2429/43581
  • Erfan Baghani, "Third Harmonic Generation in Cubic Group Crystal Lattices", Master of Science dissertation, Sharif University of Technology, 2007.







Email: ebaghani@gmail.com